The present invention relates to pick-up trucks having composite cargo boxes, and more particularly to a method for attaching cosmetic body panels thereto.
The metal cargo box of a pick-up truck is subjected to extreme wear over the life of the vehicle, in that this is where a wide spectrum of cargo interacts with the structural members of the truck. One solution to the wear problem has been the introduction of Polymeric bed liners which line the cargo box with the objective of protecting the metallic structural members of the truck from the deleterious effects of cargo interaction. As a practical matter, however, bed liners can actually facilitate corrosion of painted steel members due to water entrapment, and cargo impacts can contribute to corrosion. Indeed, even with a bed liner, the cargo box can be expected to often be the first metal part of a truck which fails over time. Accordingly, a welcomed recent major advance in pick-up truck design has been the introduction by General Motors Corporation of a composite cargo box. Because the cargo box is composite, there is no steel to rust, and there is no need for a bed liner. Advantages of a composite cargo box include weight reduction, durability, low maintenance, and freedom from denting and cargo loading worries.
Composite cargo boxes (and the inside of the tailgate) are formed by a structural reaction injection molding (SRIM) process consisting of a 50/50 mix of urethane and glass fiber. An adhesive, for example PLASTILOCK 731-SI of Sovereign Specialty Chemicals, Inc. of Chicago, Ill. which is a two-part modified epoxy, is used to secure the composite cargo box to the truck frame.
Attached to the cargo box are the cosmetic body panels (fenders). The cosmetic body panels, and the outside of the tailgate, are made of reinforced reaction injection molded (RRIM) materials, chiefly polyurea with mica filler. The attachment is effected by an interference fit between the sidewall of the cargo box and the cosmetic body panel, as well as by a number of retainers.
An example of the current methodology for attachment of cosmetic body panels to a composite cargo box is shown herein at FIGS. 1 through 3 and is described in detail in U.S. Pat. No. 5,228,742 to Johnson et al., the disclosure of which is hereby herein incorporated by reference.
Referring now to FIGS. 1 and 2, the composite cargo box 10 integrally includes, at the top thereof, a peripheral top rail 16F including a horizontal top rail portion 16H and a vertical top rail portion 16V. An L-shaped lip 12 has a base portion 14 which is integral with the cargo box sidewall 16 at the vertical top rail portion 16V, and further has an upstanding wedge shaped portion 20, preferably in the form of a plurality of wedges (best seen at FIG. 2) which is integral with the base portion. The wedge shaped portion 20 is separated from the vertical top rail portion 16V of the cargo box sidewall so as to form a slot 22 at the base portion 14. The integral lip 12 is discontinuous, in that about every 5 inches it is punctuated by periodic notches 24 of about 1.5 inches in length. The cosmetic body panel (fender) 26 has along its upper inside edge a plurality of tabs 28 which are configured to interference fit into the slot 22, wherein there is a tongue 30 between each tab, and wherein each tongue fits into a respective notch 24. As shown at FIG. 2, this interference fit secures the cosmetic body panel to the composite cargo bed along the peripheral top rail 16F of the sidewall; and fasteners 32 supplement the attachment of the composite body panel to the composite, cargo bed.
FIG. 3 depicts a tool for forming the composite cargo box 10, wherein first and second tools 34, 36 collectively form a mold 38. It will be noted that in order to form the integral lip 12 (inclusive of the base portion 14 and the wedge shaped portion 20), a blade 40 of the first tool 34 is necessary. The blade 40 is affected by each cycling of the mold 38, wherein the formed cargo box 10 tends to abrade the blade each time a part is made. Accordingly, the blade 40 requires particular attention and more maintenance than the mold in general.
Accordingly, it would be beneficial if somehow sidewall lips of a composite cargo bed could be provided without a blade being associated with the mold.
The present invention is a method and apparatus for attaching a cosmetic body panel to a composite cargo box without inclusion of a conventional integral lip.
According to the method of the present invention, the cargo box sidewalls are formed without integral lips. A lip member is bonded to the peripheral top rail at the top of the sidewalls so as to mimic the surface contour (geometry) of a conventional integral lip, including the slot, notches and wedge shape thereof for like attaching of a cosmetic body panel thereto.
The lip member is composed of sheet metal having a base wall; an attachment wall upstanding in relation to the base wall; and a wedge shaped wall connected with the base wall so as to define a wedge shaped surface contour. The wedge shape wall is separated from the attachment wall so as to thereby define a slot therebetween. Each of the slot and wedge shaped wall are configured to mimic corresponding structures of a conventional integral lip of a conventional composite cargo box. To mimic notches of a conventional integral lip, a single lip member may be notched to periodically remove, along the attachment wall, the base and wedge shaped walls, or, alternatively, a plurality of mutually separated lip members may be used.
Further according to the method of the present invention, the attachment wall is attached to the vertical top rail portion of the peripheral top rail of the composite cargo box sidewall. The preferred attachment modality is via a suitable, permanent adhesive. The preferred adhesive is a two-part epoxy which requires no composite surface treatment to be adhesively effective.
In operation, a composite cargo box is formed having sidewalls absent conventional integral lips. At least one lip member is bonded to each sidewall at the peripheral top rail thereof, wherein either a plurality of lip members are provided and mutually separated from its neighbors so as to provide a notch at each of the separations, or a single lip member is provided having a plurality of notches formed therealong. A cosmetic body panel of conventional design is then attached by interference fit to the slot and notches of the at least one lip member.
Accordingly, it is an object of the present invention to provide a composite cargo box formed without conventional integral lips, the sidewalls thereof having at least one lip member bonded thereto.
This and additional objects, features and advantages of the present invention will become clearer from the following specification of a preferred embodiment.